Modeling And Analysis Of Polypropylene Process In Steady And Dynamic State

The modeling of the propylene polymerization process and the optimal control of product properties during grade transitions are the most significant projects of polypropylene. The polymer reaction is a high complexity, high coupled and high no-linearity process, there is no way to measure the control target and its key variable on line, this leads the simulation and modeling for polymer reaction process very difficult. In present dissertation, a comprehensive steady state and dynamics model for liquid phase bulk propylene polymerization plant in BYPC was developed by using Polymers Plus and Dynamics Plus of ASPEN TECH.The steady state model contains gas-liquid equilibrium, material balance and energy equilibrium, kinetics of polymerization, and the correlative equation for molecular weight and Melt Index.Though there isn't unanimous agreement on the mechanism of polymerization of propylene, we adopted the most popular theory—combination polymerization theory and proposed some assumptions on the kinetic reactions to facilitate the model. Based on analysis of collection of literature and the plant operating data, we suggested the reaction mechanism for Hypol process liquid phase bulk propylene polymerization using TK-AT-OF catalyst and the number of catalyst site type , and established the reaction kinetics at each site type.By the steady state model, we may predict product property and develop new polypropylene grade;from the steady state model, we developed dynamics model, by the dynamics model ,we may monitor and control the product quality target which could not been measured on line to optimize grade transition approach and reduce the transition time.Based on the steady state model , we analyzed the affection of hydrogen flow rate, reaction temperature and residence time to the polymer production Melt Index; Based on the dynamics model, we built the grade transition step.